Members DarkLlama Posted March 10, 2009 Members Share Posted March 10, 2009 Thats pretty much it. I picked up a half sanded MIM Jazz body and I'm going to finish the project. What are the ups and downs to both nitro and poly? Any opinion would be great. Thanks. Link to comment Share on other sites More sharing options...
Members ThudMuffin Posted March 10, 2009 Members Share Posted March 10, 2009 Other than nitro being a huge pain in the ass? I know some will say it makes the body more resonant or some-such, but meh, I've refinned in nitro from poly, and noticed nothing. Maybe more discerning ears can tell? Link to comment Share on other sites More sharing options...
Members WRGKMC Posted March 10, 2009 Members Share Posted March 10, 2009 I would say drying time and ding repairability are definate plusses for laquer, durability is a plus for polyuerothane. Both contain polymers. Heres some articles. Its really a personal choice. Heres a quote from an article I highly agree with and some other simular pages. "Polyurethane isn't the name of a kind of finish, merely the name of one particular ingredient, a plastic resin, in a number of kinds of finishes. Finishes that contain only polyurethane as the resin are almost always two part, or have specific curing properties, as requiring UV light or moisture. There are only a very short list of such products packaged for DIY use. (I only know one such product.) Mostly what is meant in DIY usage is a varnish made using an alkyd resin modified with a bit of polyurethane resin ie. it is a uralkyd resin. This is very much like more conventional varnishes based around alkyd resin or phenolic resin (bakelite plastic) which are reacted with an oil, often linseed oil, but also tung oil or soya oil. The polyurethane addition makes this varnish softer but more abrasion resistant than the other varnishes, and poses special difficulties as far as adhesion, and the ability to be rubbed out to an even sheen, particularly a full gloss sheen. The polyrethane addition also makes these finishes subtly cloudy, creating a "plastic" look. All oil based varnishes, including poly, are quite moisture resistant and resistant to household chemicals. In my personal opinion, the only use for polyurethane varnishs is on floors where the abrasion resistance matters. Otherwise, conventional resin varnish is easier to use, and more attractive. Nitrocellulose lacquer is an evaporative finish that doesn't cure, it just dries as the solvent evaporates. The solvent can redissolve it at any time, and does so at one particularly advantageous time, when the next coat is applied over the previous ones. That means that the coats melt together essentially making a single coat. Lacquer is dramatically harder than poly which means it rubs out much more easily. It is a little more resistant to household chemicals than shellac, and similar to shellac in water resistance. Most lacquer is designed for spray application, though there are several brands of "brushing" lacquers, who solvents are chosen to take long enough to dry that with quick work, they can be applied by brush. There are waterborne finishes sometimes labeled lacquer or polyurethane. In both cases the dominant resin acyrlic, with small amounts of polyurethane for a touch more abrashion resistance than acyrlic alone. But these waterborne products are more alike than different, with the names being mostly marketing ploys". http://www.taunton.com/finewoodworking/pages/w00060.asp http://www.frets.com/FRETSPages/Luthier/Technique/Finish/Lacquer/DropFill/dropfill.html Musical tone may be be another consideration. http://www.edroman.com/techarticles/polyvsnitro.htm Link to comment Share on other sites More sharing options...
Members charSTAR Posted March 11, 2009 Members Share Posted March 11, 2009 The Nitro is supposed to let the wood "age" over time and let the sap evaporate and make the wood more resonant, where the poly seals the wood like a ziplock baggie, the sap stays in, and the guitar never cures.On a $1000 plus dollar guitar, I believe it makes a difference if done correctly.On a $300 guitar, it is just a pain in the ass to work with compared to poly. Link to comment Share on other sites More sharing options...
Members normh Posted March 11, 2009 Members Share Posted March 11, 2009 Poly cures much faster than lacquer. Overnight for Poly (two hours to touch) whereas lacquer dries to touch in 20 minutes to an hour, but takes forever, depending on temperature and humidity, to cure enough that you do not get imprints from a towel set on the finished surface. Poly is more temperature tolerant when spraying than lacquer is. Lacquer coloring is very susceptible to the mixture of solvents, retarders, and accelerants. In other words, If you mix a quantity of Nitro with analyne dyes (basically leather dye) and mix a small portion of that with 20% lacquer thinner, wait three days sand it down for the next coat, but do not measure the thinner correctly and mix 22%, the shade will be different. As with all colors, the darker colors are more noticeable. If you heat cure lacquer, you run into many different problems. You may have a perfect shoot, and a 45 minute dry when you move the piece to a heat closet. Later, the heavier solvents may have evaporated and left a few bubbles that were not there when you put it in the heat closet. If you raise the temperature above about 105.5 F, the lacquer will stop curing until you raise the temp to above 202 F of below 90 F for twenty minutes. If you lacquer over inlays, the temperature difference between the inlay, the glue (especially epoxy) and the wood can, and usually will, leave rings that can be hard to rub out. It is difficult to rub out clear lacquer without scratches. Lacquer is easy to repair by either shooting a new coat or spraying with Lacquer thinner, or drop filling, but takes longer than Poly. It is said that Poly can not be repaired. Poly can be repaired, but it is much more difficult than lacquer and if incorrectly done, poly will peel. If done correctly, it is stable. Lacquer will allow the wood to breath, whereas poly encases the wood in a plastic sheath allowing the wood to breath only from the unfinished surfaces. Poly is more durable than lacquer, but depending on the type used, may be more susceptible to damage from some commonly used cleaners. Lacquer is more susceptible to heat damage than poly. Lacquer requires many more coats to finish than poly. I can not tell a difference in sound between poly and lacquer it both are finished with thin coats. Link to comment Share on other sites More sharing options...
Members musicdog400 Posted March 11, 2009 Members Share Posted March 11, 2009 I've been looking for finishing instructions specific to poly. I have only used spray poly from the hardware store, it is for prototypes I build that don't need to look good, just have some protection. What I did in the past was spray a coat, dry for 30 min, 0000 steel wool, and repeat 4 times. I also did a tung oil finish once, very easy. Link to comment Share on other sites More sharing options...
Members normh Posted March 11, 2009 Members Share Posted March 11, 2009 Sand entire piece of wood to 220 grit, seal. Spray coat of poly and let dry overnight, scuff sand with 400 grit, clean with naptha, let dry for an hour. Use either tack rag or air to blow off, spray again. Repeat scuff sand and respray as many times as needed. I only do three coats total. When scuff sanded the poly is an ugly gray, but it clears with next shoot. When last coat dry, polish with 000 or finer steel wool and polish. Link to comment Share on other sites More sharing options...
Members bartak101 Posted March 11, 2009 Members Share Posted March 11, 2009 make sure the poly has no matting agents in it otherwise repeated coats will cause a fog. Make sure you use 99% gloss as top coat. I use 2 pac poly for furniture and guitar finishes and find it easy to apply and get to a high quality finish. The last guitar I spayed only had about 7/8 coats of clear which only added up to about .4mm of finish, much thinner than the poly you find on some guitars. So I can't see it having a negative effect on tone. Link to comment Share on other sites More sharing options...
Members DarkLlama Posted March 12, 2009 Author Members Share Posted March 12, 2009 thanks everyone...Lots of good advice. I think I'm just going to go with poly, being that this is my first project and all. You've all successfully scared me off of nitro lol. Link to comment Share on other sites More sharing options...
Members wikwox Posted March 14, 2009 Members Share Posted March 14, 2009 Lacquers a pain but Gibson and other hi-enders like it.I've seen a few excellent repairs and some stinkers as well. Poly's tough but I believe the "damps vibration" talk, especially for a thicker coating. Anybody tried varnish? It can be fairly tough especially in the "marine" variety and I believe most bowed intruments use it exclusively. Like lacquer it hi-lites wood grain nicely. Link to comment Share on other sites More sharing options...
Members Belva Posted March 14, 2009 Members Share Posted March 14, 2009 I plan on trying acrylic laquer for my next project. Many colors available and the recent Duplicolor thread made me think this may be a good choice. Plus I found a color I like. Sorry, no pics until it's done. Link to comment Share on other sites More sharing options...
Members Rob14 Posted March 15, 2009 Members Share Posted March 15, 2009 Lacquers a pain but Gibson and other hi-enders like it.I've seen a few excellent repairs and some stinkers as well. Poly's tough but I believe the "damps vibration" talk, especially for a thicker coating. Anybody tried varnish? It can be fairly tough especially in the "marine" variety and I believe most bowed intruments use it exclusively. Like lacquer it hi-lites wood grain nicely. I think you're probably right about poly damping vibration if too thick, but on a solid body guitar amplified, I doubt anyone could tell the difference. Marine varnish could be OK, I've never tried it, but many modern marine varnishes contain poly, just usualy mixed with an oil base such as tung.French polish (shelac) is still preferd by some classical instrument makers and probably has the least effect on resonance of any of the hard finish coatings.it can also be sprayed or brushed on as well as the traditional rubbed on method and it polishes up well with a classy luster. It can be easily recoated at any time too. Just don't stand anything hot on it!There have been some good reports on MINWAX rub on poly on this site and I've just bought some to try. Might be worth considering? Link to comment Share on other sites More sharing options...
Members Rob14 Posted March 15, 2009 Members Share Posted March 15, 2009 Check out "My Project post by TFM53, re rub on poly.His results look great. Link to comment Share on other sites More sharing options...
Members Belva Posted March 15, 2009 Members Share Posted March 15, 2009 I think you're probably right about poly damping vibration if too thick, but on a solid body guitar amplified, I doubt anyone could tell the difference. Marine varnish could be OK, I've never tried it, but many modern marine varnishes contain poly, just usualy mixed with an oil base such as tung. French polish (shelac) is still preferd by some classical instrument makers and probably has the least effect on resonance of any of the hard finish coatings. it can also be sprayed or brushed on as well as the traditional rubbed on method and it polishes up well with a classy luster. It can be easily recoated at any time too. Just don't stand anything hot on it! There have been some good reports on MINWAX rub on poly on this site and I've just bought some to try. Might be worth considering? Anybody tries to stand anything hot on one of my guitars will be rendered incapable of reproduction! Link to comment Share on other sites More sharing options...
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